The development of cardiac hypertrophy in response to a sustained stress is a fundamental property of the human heart. Although regression of this hypertrophy may occur following removal of the inciting stress, critical determinants of the rate and completeness of this process are poorly understood. The goal of this research proposal is to identify these determinants, and assess their influence on the extent to which myocardial hypertrophy in man is a reversible process. Specific questions to be answered include: (1) Are the pattern of hypertrophy (eccentric vs. concentric) and nature of the inciting stress (pressure vs. volume overload, acute vs. chronic) important determinants of reversibility? (2) What is the relation between contractile performance and reversibility? (3) What is the relation between the altered compliance which may accompany hypertrophy, and reversibility of that hypertrophy? (4) Are renal factors important determinants of regression of hypertrophy? Both invasive and noninvasive methodology will be utilized to obtain answers to these questions. Study subjects for questions 1-3 will include patients with severe left ventricular pressure or volume overload who undergo corrective heart surgery. The study population for question 4 will consist of young newly discovered hypertensives who will be followed with serial noninvasive assessment of left ventricular mass and contractile function before and during treatment of their hypertension.